[sdiy] frequency counter

[Glen]

At 06:47 PM 6/25/04 , Mark Romberg wrote:

>anyone know of a simple-ish frequency counter circuit?  beginning to 
>realize im going to need one to tune oscillators and things in the 
>analog world as i dont have perfect pitch :/
>saw one on sdiy.org, but no schematics or source code for the uC.

If you already have one synth which is known to be in tune, you can use an
oscilloscope in X-Y mode to compare signals between the two. This forms a
lissajous pattern on the scope. If the two signals are tuned to a perfect
interval, such as an octave or unison, the lissajous pattern will be
stationary. If there is any amount of imperfection in the tuning ratio, the
pattern will move around on the screen. The visual feedback helps quite a
bit, especially if your hearing or sense of pitch isn't quite perfect--or
if you simply want to impress any visitors.  ;)

This works far, far better than the frequency counter, but it requires
having some reference signals which are known to be in tune. You might get
away with creating some reference tones as WAV files, and use those to tune
to. You might also find an oscilloscope program to run on your computer
which offers X-Y mode, if you don't have a real oscilloscope.

Of course, there are also some guitar tuning programs available for
personal computers. I haven't tried any of them, so I don't know how well
they actually perform.

The main thing to realize is, frequency counters aren't well suited to
tuning synths. If you bought one just for that purpose, it would be a sad
waste of your money. However, if you get into serious Synth-DIY, you will
eventually want an oscilloscope--even if you can often work around not
having one.


later,
Glen